I'm not familiar with the Hensel, but I might be able to explain power distribution on this style of strobe. I have several Norman power packs and have used most of the pro systems (Dynalite, Speedotron, Profoto, etc) at one time or another. Basically, they all work the same. They usually have "channels" which may or may not have equal power. The channels work independently, unless you do something that ties them together. For example, the "A" channel might have 1200ws (watt seconds) available, while the "B" channel has only 800ws. Each channel has a seperate switch that further enables you to cut the power in half AND/OR a variator (like a dimmer) that lets you control the output seamlessly. (I have 3 Norman packs with that combo). If you plug one head into the 1200ws side, you get up to 1200ws through that head (if you have the power selector switch set to 1200ws). If you plug another head into the same channel (most channels have 2 or 4 outlets), you split the power between the two heads evenly. If you put one head on each channel, you get 1200ws from one, and 800ws from the other. If you cut the power level switches down on both channels, that changes to 600ws and 400ws respectively. Every combination of multiple heads into one channel, divides the power output evenly amoung however many heads are in that channel (sometimes we use an extra head aimed off to the side as a "dump" head, just to lower the output levels on whatever else is plugged into that channel. (This is all about controling the "power" ratios and output). Now most of these kinds of packs have another switch that joins the two channels for maximum (and symetrical) power output to all the outlets together like they were one big channgel. In other words, by throwing the switch on my pack I can get a total of 2000ws out of one head, or 1000ws from each of two heads, 500ws from each of 4 heads, 660ws out of each of 3 heads, etc. (And not to make this too much more confusing, on some packs, including my Normans, the "join" switch is not a switch, but one of the outlets, that when occupied by a head cable, accomplishes the task of joining the two channels of the pack. This is all really easy when you've been working with this type of pack for a while, but is total different from the monolight method.
Now one more thing. Even though you have the power distribution under control, that does not necessarily mean the heads will put out exactly the same level of light. All you're doing here is controling the power levels, not the light output. All things being equal, you would have the same amount of light at the same distance, but that would mean you'd have matching light modifiers (reflectors, umbrellas, grids, diffusion, snoots, etc) as well as flashtubes of exactly the same age, and exactly the same length on the cables, etc. In practice, we set them up to be how we think we want them by eye, then use a flashmeter to determine if the power should be higher or lower, change the modifier, move the position of the head, etc.
Here's a couple shots illustrating a studio lighting setup, in the one on the left you can see one of the Norman packs (gray on top, black on bottom) and see the heads in use with reflectors and soft boxes. The nice thing about this type of light is amoung other things, they're not so top heavy, they're cheaper to repair, if one goes out on you, you can easily replace it in the setup, and they're more flexible to work with in the way they fit into odd places, and you can get a lot more power of of them than a monolight. The downside of course is you have to carry a pack AND a head (but extra heads are cheaper than additional monolights = more flexibilty).
Andy Pearlman Studio